Recent developments within IEEE 802 have required calls for 100 Mbps throughput in mobile environments and 1 Gbps throughput in nomadic environments. In December 2006, the 802.16m task group was formed to address these requirements. In May 2007, the IEEE 802 Executive Committee granted an 802.11 working group request to form a new study group called 802.11VHT (very high throughput) to address this requirement.
The spectrum that will be used by 802.16m and 802.11vht has not been identified yet, but it is anticipated that these throughput rates will require 80 to 100 MHz of bandwidth. Unlicensed spectrum is one of the options for both 802.16m and 802.11vht. Finally, spectrum sharing and coexistence between 802.16 and 802.11 is also a requirement of 802.16h.
A broader problem to solve is how to enable a secondary TDMA-based system such as IEEE 802.16m or 3GPP LTE to coexist with a primary CSMA-based system such as IEEE 802.11. The problem is complicated by the need to utilize multiple consecutive unlicensed channels to form a broadband channel on the order of 80-100 MHz of bandwidth. This would require the ability to enable a regular frame boundary to be established simultaneously over multiple instantiations of primary system deployments such that each primary system's CSMA MAC offers a TDMA-like frame period for the secondary system.
To reserve 80-100 MHz of spectrum, 3 or more consecutive channels must be quieted. A problem in using prior-art techniques to quiet channels one-by-one (serially) is that while one idle channel is being quieted by the single transceiver, the multiple adjacent channels may transition from busy to idle, thus giving the primary system users an opportunity to grab one of the idle channels before the secondary system transceiver can get around to quieting each of the newly idled channels. This can cause additional latency as the transceiver must iterate the monitoring/quieting/reservation procedure until it successfully reserves all channels. Therefore a need exists for a method and apparatus to quiet multiple primary channels (e.g. WLANs) operating on an unlicensed band that alleviates the shortcomings of the prior art. Once reserved, the channels can be used by the secondary wideband system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.